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Mike Brady 60143518c2 This squashed commit comprises a long series of improvements, bug fixes, optimizations, and new feature additions:

- 48,000 frames per second operation,
 - 48k lossless stereo, 5.1 and 7.1 surround sound
 - Multichannel and multi rate operation on ALSA, PipeWire, PulseAudio, FreeBSD, stdout and unix pipe output backends.

Automatic, flexible and controllable output format (rate, sample format and channel count) selection.

Full FFmpeg integration to support transcoding, resampling, and new audio formats.

Better operation on lower powered devices down to e.g. Raspberry Pi B.

Reduced Docker image sizes with a slimmed-down FFmpeg library.

Enhanced timestamp handling for better synchronization.

Improved the sync error calculation.

A new "vernier" resampling and interpolation method for low-power CPUs.

Bug fixes and minor enhancements.

Note -- there are many breaking changes from previous versions of Shairport Sync!

2025-02-23 13:31:17 +00:00

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Working with PulseAudio or PipeWire

Many Linux systems, especially desktop Linuxes with a GUI, have PipeWire or PulseAudio installed as sound servers. PipeWire and PulseAudio are widely used and have the great advantage of being easily able to mix audio from multiple sources. The slight downside is that audio may be further processed (e.g. transcoded) on its way to the output device.

To use PipeWire or PulseAudio-based systems, Shairport Sync must be set up as a user service.

Considerations

Shairport Sync will work without modification in a PipeWire- or PulseAudio-based system if built with the default ALSA backend. This is because PipeWire and PulseAudio both provide a default ALSA pseudo-device to receive and play audio from ALSA-compatible programs.
Shairport Sync can be built with "native" PipeWire or PulseAudio backends by adding the --with-pipewire or --with-pulseaudio configuration flags when it is being built. This has the advantage of bypassing the ALSA compatability layer.
To check if PipeWire support is built into Shairport Sync, check that the string PipeWire is included in the version string. (Enter $ shairport-sync -V to get the version string.) Similarly, the version string will include PulseAudio if the PulseAudio backend is built in.
Remember to specify which backend Shairport Sync should use in the configuration file or on the command line.

Automatic Startup of Shairport Sync

The main thing to remember about PipeWire and PulseAudio sound servers is that the services they offer only become available when a user logs in -- that is, they are set up as user services. Shairport Sync relies on them, so it must also be set up as a user service; it can not be set up as a system service because the PipeWire or PulseAudio services needed by Shairport Sync are not available when system services are launched just after system startup.

Starting Shairport Sync as a User Service

To make Shairport Sync start as a user service, (assuming you built and installed Shairport Sync using the BUILD.md guide), ensure you are logged in as the appropriate user and enter:

$ systemctl --user enable shairport-sync

Make sure it is not enabled as a system service:

# systemctl disable shairport-sync

and then reboot.

Problems with User Service

Shairport Sync will function perfectly well as a user service, but there are a number of things to bear in mind:

The AirPlay service will only be available when the user is logged in. When the user logs out, Shairport Sync will terminate and the AirPlay service will disappear.
If the Linux system is a desktop Linux with a GUI, audio will be sent to the default output only when the user is logged in through the GUI.

Automatic user login may help address these problems.

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